The Great Attractor

The Milky Way and Andromeda galaxies are the dominant structures in a galaxy
cluster called the Local Group which is, in turn, an outlying member of the
Virgo supercluster. Andromeda--about 2.2 million light-years from the Milky
Way--is speeding toward our galaxy at 200,000 miles per hour.

This motion can only be accounted for by gravitational attraction, even
though the mass that we can observe is not nearly great enough to exert that
kind of pull. The only thing that could explain the movement of Andromeda is the
gravitational pull of a lot of unseen mass--perhaps the equivalent of 10
Milky Way-size galaxies--lying between the two galaxies.
JPEG Image (9.9 KB)

Furthermore, our entire Local Group is hurtling toward the center of the
Virgo cluster at one million miles per hour.

Virgo Cluster
The Virgo cluster lies some 50 million light years from Earth. Only the central region is
shown above, containing two giant elliptical galaxies, M84 and M86.
The visible part of the cluster is but a small portion of what
seems to be out there. Nevertheless, the Virgo Cluster, along with several other large
clusters, are in turn speeding towards a gigantic unseen mass named The
Great Attractor.
JPEG Image (27.2 KB);
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